This invention relates in general to microvalves for controlling the flow of fluid through a fluid circuit. In particular, this invention relates to an improved structure for such a microvalve that includes a venting structure that facilitates the purging of air that may be trapped within a portion of the microvalve and, as a result, might otherwise undesirably interfere with the operation of the microvalve.
Generally speaking, a micro-electro-mechanical system is a system that not only includes both electrical and mechanical components, but is additionally physically small, typically including features having sizes that are generally in the range of about ten micrometers or smaller. The term “micro-machining” is commonly understood to relate to the production of three-dimensional structures and moving parts of such micro-electro-mechanical system devices. In the past, micro-electro-mechanical systems used modified integrated circuit (e.g., computer chip) fabrication techniques (such as chemical etching) and materials (such as silicon semiconductor material), which were micro-machined to provide these very small electrical and mechanical components. More recently, however, other micro-machining techniques and materials have become available.
As used herein, the term “micro-machined device” means a device including features having sizes that are generally in the range of about ten micrometers or smaller and, thus, is at least partially formed by micro-machining. As also used herein, the term “microvalve” means a valve including features having sizes that are generally in the range of about ten micrometers or smaller and, thus, is also at least partially formed by micro-machining. Lastly, as used herein, the term “microvalve device” means a micro-machined device that includes a microvalve, but further includes additional components. It should be noted that if components other than a microvalve are included in the microvalve device, these other components may be either micro-machined components or standard-sized (i.e., larger) components. Similarly, a micro-machined device may include both micro-machined components and standard-sized components.
A variety of microvalve structures are known in the art for controlling the flow of fluid through a fluid circuit. One well known microvalve structure includes a displaceable member that is supported within a closed internal cavity provided in a valve body for pivoting or other movement between a closed position and an opened position. When disposed in the closed position, the displaceable member substantially blocks a first fluid port that is otherwise in fluid communication with a second fluid port, thereby preventing fluid from flowing between the first and second fluid ports. When disposed in the opened condition, the displaceable member does not substantially block the first fluid port from fluid communication with the second fluid port, thereby permitting fluid to flow between the first and second fluid ports.
In this conventional microvalve structure, it has been found that in some instances, a small quantity of air may become trapped within the microvalve. If this quantity of air is not purged from the microvalve, it may undesirably interfere with the efficient operation of the microvalve. To address this situation, it is known to cycle the microvalve rapidly between the closed and opened positions when the microvalve is initially turned on so as to purge any air may trapped within the microvalve therefrom. However, such initial cycling of the microvalve is also inefficient. Thus, it would be desirable to provide an improved structure for a microvalve that facilitates the purging of air that may be trapped within the microvalve.